Start Here - Code Will Set If

Diagnostic Chart:

The PCM contains an Output Driver Module (ODM) which controls seven circuits: A/C relay, air pump relay, EVAP purge solenoid, EVAP vent solenoid, fan control 1, fan control 2 and TCC solenoid. The ODM controls each of these circuits independently by controlling the circuit ground. The ODM monitors the voltage level at each of the six circuits into the PCM when the device is being commanded On or Off. When the device is commanded Off (circuit not grounded), the voltage level at the PCM should be high (ignition voltage). When the device is commanded On (circuit grounded), the voltage level at the PCM should be low. Each of the seven drivers in the ODM contains a feedback circuit used to determine if a particular circuit failed, which can be read on the Scan tool. DTC P1640 sets when any one of the seven feedback voltages is low when that device is turned Off or when any one of the seven feedback voltages is high when that device is turned On when the engine is running.

DTC PARAMETERS
DTC P1640 will set if A/C relay, air pump relay, EVAP purge solenoid, EVAP vent solenoid, fan control 1, fan control 2 or TCC solenoid feedback voltage is less than 4.0 volts when that device is commanded Off when:
^ Condition exists for longer than 6 seconds
^ Engine is running

OR

A/C relay, air pump relay, EVAP purge solenoid, EVAP vent solenoid, fan control 1, fan control 2 or TCC solenoid feedback voltage is greater than 3.5 volts when that device is commanded On when:
^ Condition exists for longer than 6 seconds
^ Engine is running

DTC P1640 diagnostic runs continuously with engine running.

P1640 is a (type C) DTC

DIAGNOSTIC AIDS

IMPORTANT: If DTC P0480, P0481 or P1860 is also set, diagnose that DTC first. P1640 will also set if a fan control 1, fan control 2 or TCC solenoid fault exists.

To locate an intermittent problem, use Scan to command each of the seven solenoids tied to the ODM circuit On and Off independently while monitoring:

A/C RELAY CKT OPEN SHORT TO GND
A/C RELAY CKT SHORT TO VOLTS

OR

AIR PUMP REL. CKT OPEN SHORT TO GND
AIR PUMP REL. CKT SHORT TO VOLTS

OR

EVAP PURGE CKT OPEN SHORT TO GND
EVAP PURGE CKT SHORT TO VOLTS

OR

EVAP VENT CKT OPEN SHORT TO GND
EVAP VENT CKT SHORT TO VOLTS

OR

FC 1 RELAY CKT OPEN SHORT TO GND
FC 1 RELAY CKT SHORT TO VOLTS

OR

FC 2 RELAY CKT OPEN SHORT TO GND
FC 2 RELAY CKT SHORT TO VOLTS

OR

TCC DUTY CYCLE OPEN SHORT TO GND
TCC DUTY CYCLE SHORT TO VOLTS

If IGN 3 fuse is open, A/C RELAY CKT OPEN SHORT TO GND, EVAP VENT CKT OPEN SHORT TO GND and EVAP PURGE CKT OPEN SHORT TO GND parameters on Scan tool will read YES.